MILWAUKEE — Scott Walker was gone. Dropped out. And in the spring of his senior year.

In 1990, that news stunned his friends at Marquette University. Walker, the campus’s suit-wearing, Reagan-loving politico — who enjoyed the place so much that he had run for student body president — had left without graduating.

To most of the Class of 1990 — and, later, to Wisconsin’s political establishment — Walker’s decision to quit college has been a lingering mystery.

Not even his friends at Marquette were entirely sure why he never finished. Some had heard that a parent had fallen ill, or maybe there was some financial strain. Others thought he had simply had enough of school.

Walker clearly liked college politics more than college itself. He had managed to line up 47 campaign endorsements, including ones from the ski team and the varsity chorus, but he had trouble showing up on time for French.

And, after four years, he had faltered on both fronts. He’d lost an ugly race for president. And he apparently had far too few credits to graduate.

Kevin Miller, who knew Walker from the Marquette Students for Life, described Walker’s thinking at the time as: “ ‘I’d rather have a full-time job and have the rest of my time to spend on politics.’ ” He said Walker intended to go back to school at some point. “I never got any indication that it was anything other than that. Or anything more than that.”

Walker’s own explanation has been short and simple. He got a job. He meant to go back. But he just never found the time.

Today, Walker, 47, is the governor of Wisconsin and a strong contender for the GOP’s 2016 presidential nomination. He is known for an astounding political hot streak: Since 1993, he has run 11 races for state legislature, county executive and governor — including a highly unusual recall election in 2012 — and he has won them all.

But before that streak came a string of defeats: the campus election, his failure to finish college and his first campaign for state office.

When Walker has told the story of his political career, he has tended to begin with his first big win in 1993, casting himself as a reluctant entrant into the world of politics.

“I always thought I’d have an interest in government, and politics and public service, but I didn’t do it right away,” he said in an interview in Philadelphia in 2013.

But then a seat came open in the state legislature, and it included the suburban neighborhood that Walker had moved to after school. “A number of my friends said, ‘Hey, you talk about all this stuff all the time, why don’t you run?’ ”

Walker was not available to comment for this article, according to a spokeswoman for his new political committee, Our American Revival. He is visiting London this week, conducting a trade mission and bolstering his foreign policy credentials.

The real story of Walker’s start in politics begins seven years earlier, when he left his home in tiny Delavan, Wis., where his father was a Baptist minister. In 1986, Walker arrived as a freshman at Marquette, a Catholic school in the heart of urban Milwaukee.

On campus, Walker made a close group of friends, who gathered weekly to watch the iconic 1980s television drama “Thirtysomething” and cook dinner on Sunday nights. They remember Walker as fun, upbeat and cautious: If you were planning a prank, you knew not to even ask him to join in.

“Kind. He’s very kind,” said Mary Riordan, a friend who is now a speech pathologist. She could remember four medical emergencies in which Walker volunteered to drive her to the hospital. There was an errant Frisbee to the mouth. Shingles. Shingles again. And a freak ankle injury, in which she tore ligaments while walking down the street.

“Scott carried me eight blocks to his car and drove me to the hospital,” Riordan said. “He became like my personal ambulance.”

But outside that group, Walker was known for something else: his political ambitions. If you met him, they were as plain as the photo of him with Ronald Reagan on his dorm-room desk.

“He would comment that, you know, ‘I’m going to be president of the United States someday,’ ” said Patrick Tepe, a former dorm mate who is now a dentist.

As a freshman, Walker was elected to the student senate. He plunged into the job, leading a hard-charging impeachment inquiry into charges of misspent money.

But in his classes, some professors said they never saw the same level of focus on schoolwork. In introductory French, for instance, Walker routinely barged into the room after the lesson had begun, loudly making excuses.

“He would talk to me, you know, say, ‘I’m very sorry, I had very important business’ ” with the student government, instructor Marc Boutet recalled. “I’m like, ‘En français! En français!’ ”

Boutet said the other students tired of the daily disruptions. They started preemptively stealing Walker’s favorite desk, so he had nowhere to sit when he arrived.

“I think I gave him a D-minus,” Boutet said, adding that he saw Walker years later, and the two laughed about the class. French, Boutet said, “was not his thing.”

Even in politics class, Walker could appear disengaged.

“He seemed utterly bored,” said Michael Fleet, who taught him in a class on the politics of the Third World. Fleet said he’d hoped to get Walker into debates with the liberals in the room. But it didn’t work. Walker would only give occasional short speeches that made conservative arguments.

“It wasn’t always on key. It wasn’t always in response to anything,” Fleet said. “He wasn’t engaged. It was like he came in with a script.”

Campaigning, on the other hand, was something Walker seemed to enjoy. But he had trouble winning. As a freshman, for instance, he ran for a higher office in student government and was defeated by a write-in candidate.

“I remember walking out and thinking, ‘Oh, we’ll never have to worry about that guy again,’ ” said Glen Barry, who had helped organize the write-in campaign. He was one of the people Walker had investigated for impeachment, and he was still upset about how he’d been treated. “We used to call him Niedermeyer,” Barry said, after the power-mad ROTC leader in the movie “Animal House.”

Then, in 1988, as a sophomore, Walker ran for student-government president against a well-known liberal student, John Quigley. Walker distributed a 20-point résumé and talked up his good deeds from high school.

“God’s honest truth,” said Quigley, remembering the epic un-hipness of their debates. “I remember him talking about being an Eagle Scout.”

In the campaign, Walker seemed to have every angle covered. There were buttons that said “Beam Me Up, Scotty!” There were slogans sprayed on campus snowbanks, with water and food coloring. The campaign even arranged a special deal at Lucci’s Pizza: Walker voters got extra cheese free.

At times, Walker’s opponents accused his campaign of going too far.

The most notable allegation was that Walker’s people had stolen copies of the campus newspaper, to keep students from reading its endorsement of the other guy. Walker’s friends say to this day that they didn’t do it.

More damaging was a flier that attacked Quigley’s ideas close to Election Day, saying that the liberal had only “vague ideals” and was destined for ineffectiveness. It was mild — at least by the standards of real-world politics — but it was enough to outrage the student newspaper.

“That was all because of something I did. Scott didn’t even know about it,” said Stephen ­Satran, who was Walker’s roommate and a fellow conservative. He said Walker would never go along with his proposals to go negative, so at the last minute he made the flier himself. “The worst thing you can say about him in that time was that he shouldn’t have trusted some of his friends. He shouldn’t have trusted me.”

Walker lost, 1,245 votes to 927. His friends say he handled it with grace, telling them the loss just meant that God had another plan.

“We are the real winners, because of the outstanding effort that we put in,” Walker wrote to Katie Cashman Flanagan, his campaign manager. Flanagan saved all three pages of the note in a scrapbook. “You have brought a great deal of good in my life.”

Satran thought Walker might not be cut out for this business after all.

“I thought that the guy was too nice to ever be successful in politics,” Satran said. Now, Walker is governor, and Satran — having worked in politics for years — is a bartender at J. Paul’s in Georgetown. “Turns out I was wrong.”

After that race, Walker was a diminished presence in campus politics.

And then he left Marquette altogether. Walker’s disappearance from campus became a mystery that his political rivals seized on. As recently as 2013, the state’s Democrats were still alleging that he might have been kicked out for election-related misdeeds. They dropped that after Marquette officials told the Milwaukee Journal Sentinel that Walker had left “in good standing.”

What friends remember is that Walker got a good job, at the American Red Cross office near campus. Some also remember hearing that one of his parents had a health problem or about financial stress on the family. A spokeswoman for Walker’s political committee declined to comment about those suggestions.

“I think I need to take this opportunity,” Riordan remembered Walker saying. “I don’t think he ever said to me, ‘I’m not going to finish school.’ I don’t think that was his intention.”

At the time, the Journal Sentinel found, Walker was not close to graduating. After four years, he was at least 34 credits short — about one-quarter of the required total away from earning his degree, according to its report. Walker’s political spokeswoman said she would not contest that finding.

He still has not found the time to finish. A spokeswoman for Walker’s state office said he is interested in a new University of Wisconsin program — begun during Walker’s tenure — that lets older students get academic credit for things they’ve learned in life. But he’s not taking courses now.

“During my senior year at Marquette University, I was offered a full-time job at the American Red Cross. I thought I would squeeze in a course here or there and finish things off in a year or two, but then Tonette and I got married,” Walker said in his State of the State speech in 2013. “Next thing you know, you’re putting all your extra time and money into your kids.”

In his first year after leaving Marquette, though, Walker wasn’t studying and he wasn’t married; he was running for office.

“In hindsight, there was really no chance,” said John Hiller, who was Walker’s campaign treasurer in his first real-world campaign.

Walker had decided to challenge Gwen Moore (D), an African American woman who represented a partly white and deeply Democratic state assembly district that surrounded Marquette, Hiller said.

Republican leaders welcomed Walker’s bid. He wouldn’t win, but he would still force Moore to spend money and time defending the seat. (Walker later moved to suburban Wauwatosa, and it was there that he won his seat in 1993.)

In 1990, the 22-year-old Walker spent days knocking on doors in the district, preaching a get-tough message. He wanted 200 more cops on the street and stronger mandatory sentences for drug dealers.

“The number one fear is crime,” he wrote in a letter to Marquette students, asking them, again, to vote for him. “For too long, we have ignored this issue and now it is time to do something about it.”

Moore, who is now a member of Congress, said: “His campaign was one big dog whistle.” She believed that Walker’s anti-crime message was a way to speak to white voters’ fears of blacks without saying them aloud. “He had sort of insinuated sort of the worst stereotypes about black people [and] innate criminality.”

Hiller, Walker’s campaign treasurer, said that Moore was entirely wrong about Walker’s message. “There was no racial angle,” he said. “It never crossed our minds.”

On election night, Walker’s chances looked so terrible that Walker and Hiller left the district and the city of Milwaukee behind. They started driving to Madison, the state capital, to attend parties for other Republicans who had a chance.

Then, for a minute, something strange happened.

“We’re listening to election returns on the radio, and the guy comes on: ‘In a surprise in the [7th District], Scott Walker is ahead of Gwen Moore,’ ” Hiller said. “Literally, I pulled off the road.”

The two young men sat there on the shoulder, blindsided by the idea that Walker — a politician who hadn’t won anything he really wanted — might be about to win.

“Should we go back?” Hiller remembered saying.

But where would they go back to? There was no Walker campaign party in Milwaukee. Most of the campaign was right there in the car.

As the two sat stunned by the possibility of victory, the man on the radio spoke again.

“Within two minutes, he came back. He said, ‘Sorry, I transposed the names,’ ” Hiller said.

Walker was not winning after all. He was, in fact, getting shellacked. In the final tally, Moore won by a margin of 38 points, 69 percent to 31 percent.

In the car, Hiller remembers the two men laughing. They got back on the highway to Madison. And that was the last time Scott Walker lost an election.